PTFE Fabric Testing

PTFE fabric testing mainly conducts scientific testing and analysis on thickness and mass per unit area, tensile strength and elongation at break, tearing strength, air/moisture permeability, chemical corrosion resistance and surface characteristics, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Thickness and mass per unit area: As basic physical indicators, the thickness is usually measured with a standard thickness gauge under a specific pressure by taking samples at multiple points and averaging them, with the unit usually being millimetres (mm). The mass per unit area refers to the mass of the fabric per unit area, calculated by precisely cutting a sample of a known area and weighing it, with the unit being grams per square metre (g/m²). This indicator directly affects the mechanical properties and cost of the material.

Tensile strength and elongation at break: This test evaluates the tensile resistance and extensibility of the PTFE fabric in the longitudinal (warp) and transverse (weft) directions. A universal material testing machine is used, and the test is carried out according to the specimen size and tensile speed specified by the standard. The maximum force and elongation percentage at the breakage of the specimen are recorded, which are the key basis for judging its mechanical load-bearing capacity and flexibility.

Tearing strength: Measures the ability of the PTFE fabric to resist the propagation of tears, usually tested by the trapezoid method, tongue method or Elmendorf falling pendulum method. This property is crucial in application scenarios where there are cuts or where snagging is likely to occur (such as sealing gaskets and flexible connectors), and is directly related to the durability and safety of the product.

Air/moisture permeability: For PTFE fabrics with specific uses, such as garment fabrics or filter materials, their gas or water vapour transmission performance needs to be evaluated. The air permeability test mostly adopts the differential pressure method, while the moisture permeability commonly uses the moisture-permeable cup method, characterized by measuring the amount of gas or water vapour passing through a specimen of a unit area per unit time under a unit pressure difference.

Chemical corrosion resistance: Polytetrafluoroethylene (PTFE) itself is famous for its excellent chemical inertness, but the fabric made from it may be affected by processing aids or the structure. The test method includes soaking the sample in chemical media such as acids, alkalis and organic solvents of specific concentrations and temperatures for a certain time, and then observing and detecting the change rates of its appearance, dimensions, mass and mechanical properties.

Surface characteristics: Including the hydrostatic pressure test to evaluate the penetration resistance of the fabric; the surface wettability test (contact angle measurement) to judge its hydrophobic and oleophobic performance; and the friction coefficient test, which is particularly important for the application of the PTFE fabric in conveyor belts or sliding components.

Testing Scope

Industrial sealing and gasket materials: Used for sealing gaskets and packings at pipe flanges, reactors, pumps and valves. The testing focus is on their compression resilience, creep relaxation performance, resistance to medium penetration, and long-term stability under extreme temperatures and pressures, ensuring no leakage risk.

High-temperature filter materials: Applied to the filter bags of baghouse dust collectors in the cement, metallurgy and waste incineration industries. In addition to the conventional mechanical properties, the testing scope focuses more on the dimensional stability at high temperatures, acid and alkali corrosion resistance, filtration efficiency, dust release rate and service life evaluation.

Electrical insulation materials: Used as insulation liners or sleeves of motors, cables, transformers and other equipment. The core testing items include the electric strength (breakdown voltage), volume resistivity and surface resistivity, dielectric constant and dielectric dissipation factor, and the insulation performance retention rate in humid and high-temperature environments also needs to be evaluated.

Protective clothing and fabrics: Used to make chemical protective clothing, firefighting suit liners or the waterproof and breathable layers of high-end outdoor clothing. Testing needs to cover the flame retardancy (such as the limiting oxygen index), resistance to liquid chemical penetration, moisture permeability, hydrostatic pressure resistance and the abrasion resistance tests of the ergonomic zones.

Building and membrane structure materials: Used for the membrane structure roofs of large stadiums and transportation hubs. The testing scope includes UV aging resistance, long-term weather resistance, self-cleaning performance, strength against wind and snow loads, and the peeling strength at the seams, ensuring structural safety and durability.

Food and pharmaceutical industry components: Used in occasions that directly or indirectly contact products, such as conveyor belts, drying belts and packaging materials. Testing must comply with the relevant hygiene regulations, such as FDA and EU 10/2011, carrying out extractable tests and microbial limit tests, and ensuring no migration of toxic substances.

Testing Methods

Physical property test method: The thickness is measured in accordance with standards such as GB/T 3820 and ISO 5084; the mass per unit area is determined in accordance with GB/T 4669 and ISO 3801; the tensile strength and elongation are tested in accordance with GB/T 3923.1 and ISO 13934-1; the trapezoid tearing strength is tested in accordance with GB/T 3917.3 and ISO 13937-3. All of these are basic and key quantitative analysis methods.

Chemical stability evaluation method: With reference to methods such as ASTM D543 and ISO 175, the specimen is immersed in standard chemical reagents (such as concentrated sulphuric acid, sodium hydroxide solution and acetone). After the specified temperature and duration, its corrosion resistance grade is systematically evaluated through the mass change rate, strength retention rate and appearance change.

Thermal performance analysis method: Thermogravimetric analysis (TGA) is used to determine the thermal decomposition temperature of the material; differential scanning calorimetry (DSC) is used to analyse its melting point and crystallinity; thermomechanical analysis (TMA) is used to measure its coefficient of thermal expansion. These methods are crucial for judging the upper limit of the PTFE fabric in high-temperature applications.

Electrical performance test method: The electric strength test is carried out in accordance with GB/T 1408.1 and IEC 60243-1; the volume resistivity and surface resistivity tests are carried out in accordance with GB/T 1410 and IEC 60093; the dielectric properties are measured in accordance with GB/T 1409 and IEC 60250. The tests are usually carried out in a standard temperature and humidity chamber to simulate different environmental conditions.

Weather resistance and aging test method: A xenon lamp aging test chamber (with reference to GB/T 16422.2 and ISO 4892-2) is used to simulate the full-spectrum radiation of sunlight; or a UV aging chamber is used for accelerated aging tests. Samples are regularly taken to detect the colour change, strength loss and surface chalking, so as to predict the outdoor service life.

Dedicated filtration performance test method: For PTFE fabrics for filtration, in accordance with standards such as GB/T 6719 and ISO 11057, a dust filtration efficiency test bench is used to measure its collection efficiency for dust of a specific particle size distribution (such as PM2.5), the filtration resistance and the resistance recovery rate after cleaning, comprehensively evaluating its filtration performance.

Testing Standards

Domestic Standards:

1. GB/T 3923.1-2013, Textiles — Tensile properties of fabrics — Part 1: Determination of breaking force and elongation at breaking force using the strip method

2. GB 18401-2010, National general safety technical code for textile products

3. GB/T 3920-2024, Textiles — Tests for colour fastness — Colour fastness to rubbing

4. GB/T 3921-2008, Textiles — Tests for colour fastness — Colour fastness to washing with soap or soap and soda

International Standards:

1. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

2. ISO 105, Textiles — Tests for colour fastness

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Universal material testing machine: The core mechanical property testing equipment, equipped with a high-precision force sensor and extensometer, which can carry out various tests such as tensile, compression, bending, tearing and peeling. The equipment needs to comply with calibration specifications such as ISO 7500-1, ensuring the accuracy and repeatability of the test data. It is the basis for evaluating the mechanical strength of the PTFE fabric.

Thickness gauge and electronic balance: The thickness gauge needs to adopt a contact flat probe and apply a standard pressure (such as 2 kPa specified in GB/T 3820) for multi-point thickness measurement. A high-precision electronic balance (accuracy 0.001 g or higher) is used to weigh the sample, and combined with a standard sampler, the mass per unit area data is precisely calculated.

Air/moisture permeability tester: The air permeability tester is usually of the differential pressure type, such as the Textest FX 3300 model, which can measure the air permeability under various pressure differences. The moisture permeability tester (moisture-permeable cup) needs to be placed in a constant temperature and humidity chamber, and the water vapour transmission amount is calculated by weighing the mass change of the moisture-permeable cup within a specified time.

Electrical performance test system: Including a high-voltage breakdown device (for the electric strength test), a high-resistance meter (for the resistivity test) and a precision LCR meter or dielectric spectrometer (for the dielectric property test). All tests need to be carried out in a shielded room, using standard electrodes and fixtures, to exclude environmental interference.

Environmental aging test chamber: The xenon lamp aging test chamber can simulate the comprehensive environment of full-spectrum sunlight, temperature, humidity, rain and other factors. The UV aging chamber mainly simulates the influence of the ultraviolet band. The equipment needs to precisely control the irradiance, black panel temperature and chamber humidity, so as to achieve the comparability of the accelerated aging tests.

Chemical and thermal analysis instruments: Fourier transform infrared spectroscopy (FTIR) is used for the identification of the material composition; thermogravimetric analysers (TGA) and differential scanning calorimeters (DSC) are used for the thermal stability analysis; scanning electron microscopes (SEM) can be used to observe the fibre morphology, cross-section structure and the micro changes after aging and corrosion.